Revert remove dead hole check logic

src/crankshaft/mips64/lithium-codegen-mips64.cc

Index: src/crankshaft/mips64/lithium-codegen-mips64.cc
diff --git a/src/crankshaft/mips64/lithium-codegen-mips64.cc b/src/crankshaft/mips64/lithium-codegen-mips64.cc
index 64c42c69d73069b027d35ee0c9405ecd3ee36ea9..0730cb9d34691c086c48b3ee982ad29afa968555 100644
--- a/src/crankshaft/mips64/lithium-codegen-mips64.cc
+++ b/src/crankshaft/mips64/lithium-codegen-mips64.cc
@@ -2607,14 +2607,40 @@ void LCodeGen::DoLoadContextSlot(LLoadContextSlot* instr) {
   Register result = ToRegister(instr->result());
 
   __ ld(result, ContextMemOperand(context, instr->slot_index()));
+  if (instr->hydrogen()->RequiresHoleCheck()) {
+    __ LoadRoot(at, Heap::kTheHoleValueRootIndex);
+
+    if (instr->hydrogen()->DeoptimizesOnHole()) {
+      DeoptimizeIf(eq, instr, DeoptimizeReason::kHole, result, Operand(at));
+    } else {
+      Label is_not_hole;
+      __ Branch(&is_not_hole, ne, result, Operand(at));
+      __ LoadRoot(result, Heap::kUndefinedValueRootIndex);
+      __ bind(&is_not_hole);
+    }
+  }
 }
 
 
 void LCodeGen::DoStoreContextSlot(LStoreContextSlot* instr) {
   Register context = ToRegister(instr->context());
   Register value = ToRegister(instr->value());
+  Register scratch = scratch0();
   MemOperand target = ContextMemOperand(context, instr->slot_index());
 
+  Label skip_assignment;
+
+  if (instr->hydrogen()->RequiresHoleCheck()) {
+    __ ld(scratch, target);
+    __ LoadRoot(at, Heap::kTheHoleValueRootIndex);
+
+    if (instr->hydrogen()->DeoptimizesOnHole()) {
+      DeoptimizeIf(eq, instr, DeoptimizeReason::kHole, scratch, Operand(at));
+    } else {
+      __ Branch(&skip_assignment, ne, scratch, Operand(at));
+    }
+  }
+
   __ sd(value, target);
   if (instr->hydrogen()->NeedsWriteBarrier()) {
     SmiCheck check_needed =
@@ -2629,6 +2655,8 @@ void LCodeGen::DoStoreContextSlot(LStoreContextSlot* instr) {
                               EMIT_REMEMBERED_SET,
                               check_needed);
   }
+
+  __ bind(&skip_assignment);
 }